Meta Pixel and Conversions API with deduplication

Meta treats a browser event and a server event as the same event when they come from the same Pixel with the same event_name and the same event_id, and arrive within 48 hours of each other. It keeps one and drops the other.

• The event name must match exactly, for example Purchase in both.
• The event_id must be identical in both, so it has to be created once, in the browser, and shared.
• The _fbp and _fbc cookies help Meta match the server event to the visitor. Because the GA4 hit goes to your own subdomain, the browser sends these cookies with it and the server tag can read them.

Generate a unique ID when the event happens and push it to the dataLayer together with the event.

const eventId = crypto.randomUUID();

window.dataLayer = window.dataLayer || [];
window.dataLayer.push({ ecommerce: null });
window.dataLayer.push({
  event: 'purchase',
  event_id: eventId,
  ecommerce: {
    transaction_id: 'T-10293',
    value: 129.90,
    currency: 'EUR',
    items: [{ item_id: 'SKU-1', item_name: 'Shoes', price: 129.90, quantity: 1 }]
  }
});

1. 1 In the web container create a Data Layer Variable with the name event_id.
2. 2 In your Meta Pixel tag (from the Community Template Gallery or your existing setup) set the event name to Purchase and the Event ID field to {{DLV - event_id}}.
3. 3 Open the GA4 event tag that sends purchase and add an event parameter event_id with the value {{DLV - event_id}}. The ID now travels to the server container inside the GA4 hit.
4. 4 Publish the web container once Preview shows the same ID in both tags.

First get an access token: in Events Manager select your Pixel, open Settings, scroll to Conversions API and click Generate access token. Keep the token secret, it can send events to your Pixel.

1. 1 In the server container go to Templates, then Tag Templates, and click Search Gallery. Add a Conversions API template, such as Meta's own Conversions API Tag or the one by Stape.
2. 2 Create a new tag from the template. Enter your Pixel ID and the access token.
3. 3 Map the event name (GA4 purchase to Meta Purchase) if the template does not do it for you.
4. 4 Make sure the event ID comes from the event_id event parameter. Most templates read it automatically.
5. 5 Trigger the tag on a Custom trigger where Client Name equals GA4 and Event Name equals purchase.

1. 1 In Events Manager select your Pixel and open Test events. Copy the test code (it looks like TEST12345).
2. 2 Paste it into the Test Event Code field of the server tag and publish, or test in server Preview.
3. 3 Trigger the event on your site. Both a Browser and a Server event should appear.
4. 4 Check that they are marked as deduplicated. If they are not, compare the event name and event_id of both.
5. 5 Remove the test event code when you are done, otherwise live events keep landing in Test events.

• The Pixel event and the GA4 hit carry the same event_id.
• The server Preview shows the Conversions API tag fired with a 2xx response.
• Events Manager shows browser and server events deduplicated.
• The test event code is removed from the live tag.